TTI studies highway congestion in more than 400 U.S. urban areas each year.

In the 2011 report, the institute found the average daily commuter in metro Denver spent an extra 49 hours on the road because of traffic congestion in 2010, up from 46 hours the previous year.

In 2005, TTI reported commuters in metro Denver endured 53 hours of extra travel time because of congestion.

The annual congestion penalty dropped to 52 hours, 49, 48 and 46 over the next four years, according to the institute’s analysis. Opening of the T-REX highway and transit project in the southeast Denver area in 2006 probably help pull down the number initially.

The economic downturn in 2008 and 2009 likely contributed as well.

With the jump back up to 49 extra hours last year, the Denver area ranked No. 8 on the congestion index among major urban areas in 2010, behind Washington, D.C.; Chicago; Los Angeles; Houston; New York; Baltimore; and San Francisco, in that order, according to TTI’s research.

Commuters in Washington spent an extra 74 hours stuck in traffic last year, while Chicago motorists were delayed an extra 71 hours on average, the report found.

The Texas institute’s report found trips of metro Denver commuters typically take 24 percent longer during peak travel periods than during “free-flow” conditions.

So, a 30-minute trip at 1 p.m. takes a little more than 37 minutes at 5 p.m., according to the report’s data.

Los Angeles ranked first among metro areas for the travel-time premium paid by commuters at rush hour over free-flowing conditions. LA motorists spent 38 percent more time commuting in peak periods when compared with off-peak travel, TTI said.

Joey Bunch has been a reporter for 28 years, including the last 12 at The Denver Post. For various newspapers he has covered the environment, water issues, politics, civil rights, sports and the casino industry.